Scientists at Wageningen University & Research (WUR) in the Netherlands have warned that climate change and genetic selection have brought root-knot nematodes further north in Europe and made cyst nematodes more difficult to control.
Together these increasingly important pests threaten the economic production of major crops such as tomato and potato. To get a clear picture of the proliferation of novel nematode species and populations and to find appropriate and sustainable solutions to these problems, WUR is launching a major research and innovation project with seventeen European partners called NEM-EMERGE. The project has been accepted as a Horizon Europe Project, resulting in €7 million of European funding.
Researcher Hans Helder explained how these nematodes work. “They drain energy from the plant, causing a plant condition referred to as ‘fatigue,’” he said. “As a result, the crop barely grows and is severely weakened leading to crop loss and hence economic damage. Annually, root-knot nematodes alone cause yield losses of several billion euros. Next to crop rotation and resistant varieties, growers currently use broad-spectrum chemicals to control these nematodes which have unwanted negative side-effects on nature and the environment.”
Both root-knot nematodes and cyst nematodes are on the rise. Helder added, “Due to global warming, our winters are becoming milder. As a result, ‘tropical’ root-knot nematodes are moving further north. Whereas they used to be found only in North Africa and southern Europe, in recent years they have also been observed in central France and halfway across the Balkans. In addition, climate change is affecting soil temperatures. At temperatures of 28 degrees or higher, some important resistance genes of crops no longer work. This line of defence that protects plants against parasites is thereby lost. Besides climate change, genetic selection is another driver that plays a role in the emergence of nematodes. Frequent use of a limited number of resistant crop varieties resulted in the rise of nematodes that are less sensitive to these resistance genes.”
The NEM-EMERGE project will investigate the current distribution of root-knot nematodes, taking soil samples from southern Turkey and Spain to northern Germany, we are going to take soil samples about every two to three hundred kilometres. “Based on the resulting picture, modellers can predict where we can expect them in five or 15 years,” Helder explained.
The project will also look at the instability of resistance genes under high temperatures, with WUR’s Aska Goverse adding, “In the case of tomatoes, we often don’t know whether the loss of resistance is caused by temperature increase or genetic selection. That makes predicting further developments challenging. Another challenge lies in distinguishing between different populations of parasitic nematodes and determining which ones can still be controlled and which can’t.”
Ultimately the project aims to work with end-users to develop practical solutions for the control of nematode pests in an environment where chemical pesticides are increasingly restricted.